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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017-05-14 to 2017-06-28
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Analytical purity: 96.3% (based on chromatographic purity GC)
- Source and lot/batch No.of test material: A16EB1463
- Expiration date of the lot/batch: 12 September 2017 (retest date)

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature
- Stability under test conditions: stable
- Solubility and stability of the test substance in the solvent/vehicle: solubility in water: 0.2 g/L

Analytical monitoring:
yes
Details on sampling:
- Sampling method: Samples for possible analysis were taken from all test concentrations and the control at t=0 and t=48h. 2.0 mL of volume was taken from the approximate centre of the test vessels. At the end of the exposure period, the replicates were pooled at each concentration before sampling.
- Sample storage conditions before analysis: The samples were stored in a freezer. Additionally, reserve samples of 2.0 mL were taken for possible analysis.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Due to an expected low water solubility of the test item and its degradation products, a saturated solution (SS) was prepared. The preparation of test solutions started with a loading rate of 100 mg/L applying one day of magnetic stirring at room temperature to ensure full degradation of the test item to its metabolites. The obtained aqueous mixture was left to stabilize for approximately 20 minutes where after the SS was taken out by siphoning. The SS was used as the highest test concentration. Lower test concentrations were prepared by subsequent dilutions of the SS in test medium.
- Evidence of undissolved material (e.g. precipitate, surface film, etc): final test solutions were clear and colourless
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Water-flea
- Source: in-house laboratory culture with a known history
- Age at study initiation (mean and range, SD): < 24 h (from parental daphnids of more than 2 weeks old, maximum age 4 weeks)
- Method of breeding: 250 newborn daphnids (i.e. less than 3 days old) are placed into 5 liters of medium in an all-glass culture vessel. Medium is M7. After 7 days of cultivation half of the medium is renewed twice a week.
- Feeding during cultivation: fresh water algae, daily
- Feeding during test: no

ACCLIMATION
- Acclimation period: not relevant
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
180 mg/L as CaCO3
Test temperature:
18-22°C
pH:
At t=0h: 6.6 - 7.9
At t=48h: 7.4 - 8.1
Dissolved oxygen:
At t=0h: 8.8 - 9.0
At t=48h: 7.4 - 9.3
Salinity:
not relevant
Nominal and measured concentrations:
Range finder:
Nominal concentrations: 1.0 and 100% of SS
Measured concentrations (mg/L) at t=0h: 0.89 and 89 mg/L
Measured concentrations (mg/L) at t=48h: 0.71 and 84.6 mg/L

Final test:
Nominal concentrations: 0, 4.6, 10, 22, 46 and 100 mg/L
Measured concentrations (mg/L) at t=0h: 0.0048, 4.40, 9.66, 20.8, 43.3 and 92.5 mg/L
Measured concentrations (mg/L) at t=48h: 0.0045, 3.75, 8.83, 20.0, 41.6 and 95.9 mg/L

These concentrations remained stable during the 48h-test period and were 85-104% of initial at the end of the test
Details on test conditions:
TEST SYSTEM
- Test vessel: beaker
- Material, size, headspace, fill volume: 60 mL, all glass filled with 50 mL
- Aeration: not during the test
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Test medium: adjusted ISO medium

OTHER TEST CONDITIONS
- Photoperiod: 16h light daily

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Immobility was defined as those organisms which are not able to swim within 15 seconds after gentle agitation of the test container and was monitored after 24 and 48 hours of continuous treatment with the test substance.

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 1 and 100% of a SS prepared at a loading rate of 100 mg/L (setup: combined range finder/limit test)
- Results used to determine the conditions for the definitive study: yes
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
20 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: 95% C.L.: 15-26 mg/L
Details on results:
- Mortality of control: none
- Other adverse effects control: no
- Abnormal responses: none
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Mortality: no
- EC50/LC50: 48-h EC50 = 0.39 mg/L. The sensitivity of the daphnids was within the range determined with the historical data collected at Charles River Laboratorie Den Bosch.
Reported statistics and error estimates:
The 24 and 48h-EC50 values were calculated using the Spearman-Karber method (without trim) on the percentages of affected daphnids and the logarithms of the corresponding initial test item concentrations.
Validity criteria fulfilled:
yes
Conclusions:
The acute toxicity of T000749 to Daphnia magna was determined in a 48 hour static test according to OECD guideline 202. Based on nominal concentrations, the 48-h EC50 was 20 mg/L (95% confidence interval between 15 and 26 mg/L). The results of the test can be considered reliable without restriction.

Description of key information

Based on the guideline study (Bouwman, 2017) where the acute toxicity of T000749 to Daphnia magna was determined in a 48 hour static test according to OECD guideline 202, the 48-h EC50 was 20 mg/L (95% confidence interval between 15 and 26 mg/L) calculated on the basis of nominal concentration.

The results of the test can be considered reliable without restriction.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
20 mg/L

Additional information